Pneumatic operating mechanism for circuit breakers



June 9,4 1942. H. E. sTRANG 2,286,023

runuurc ormwma uncxunsu Fon Blaauw BREAKERS v Filed July 11, 1940 rooPEN c/Rcu/r /20 l BAEAKER PoslrloN 20:

g. swlrcH ITNCTYLOT: Harold E. Strang,

Patented June 9, 1942 PNEUMATIC OPERATING MECHANISM CIRCUIT BREAKERS FORHarold E. Strang, Ardmore, Pa., assigner to General Electric Company, acorporation of New York '- Application July 11, 1940, Serial No. 344,965

(Cl. 20o-82) 6 Claims.

My invention relates to pneumatic operating mechanisms having particularapplication to circuit breakers, and has particular reference tomechanisms of the trip-free type where the means to be actuated, such asa circuit breaker, can be released with respect to the actuating orclosing means during the course of the closing stroke and prior tocompletion thereof.

Heretofore, circuit breaker operating mecha nisms of the trip-free typehave generally included a collapsible linkage arrangement or the likeinvolving a more or less complicated design of toggles, levers andlatches. Since the tripfree type mechanism is required to be very rapidin action due to the fact that immediate tripiree operation of thecircuit breaker is essential when the circuit breaker is closed on afault current,V mechanical arrangements have been preferred to knownpneumatic types in view of the high speeds of operation that have beenobtained with certain mechanical mechanisms.

A principal object of the present invention is the provision of an`improved and simplified trip-free mechanism of the pneumatic or iluidoperating type that is efficient, positive and rapid in operation,rugged and compact in design and composed of comparatively few essentialoperating elements. I

lMy invention will be more fully set forth in the following descriptionreferring to the accomlpanying drawing, and the features of noveltywhich characterize my invention will be pointed out with particularityin the claims annexed to and forming a part of this specification.

Referring to the drawing, the single figure thereof is a diagrammaticview, partly in section, of a pneumatic operating mechanism for anelectric circuit breaker embodying the present invention.

The pneumatic mechanism illustrated by way of example comprisesessentially a source of operating iluid pressure indicated at I, a duidmotor or actuating means 2 and the means to be actuated comprising inthe present instance the operating means 3 of an electric circuitbreaker (not shown). preferably compressed air, although it should beunderstood that any suitable uid medium, preferably elastic, underpressure can be employed. The iiuid motor 2 comprises an operatingpiston 4 disposed for reciprocal movement in a cylinder 5 that isarranged to be in communication with the source I through a controlvalve 6. The piston I is provided with a plunger 1 operatively relatedto a lever' 8 that is ypivotally The source of fluid pressure is mountedat 9 and connected at III to the circuit breaker rod II. The pistonplunger is arranged to engage a roller I2 carried by the lever 8 and torotate the lever counterclpckwise to cause closing movement of thebreaker rod II.

In the closed circuit position shown, the breaker rod is latched inposition by a latch member I 3. The latch I3 is normally biased at I4toward latching position against a limiting stop I5 to be engaged by aroller I6 carried by the breaker rod. The breaker is normally biasedtoward open position by the usual breaker springs (not shown) so thatwhen the latch I3 is rotated clockwise about its pivot I3' to releasethe roller I6, the breaker rod II drops rapidly to its open circuitposition.

Let it now be assumed that the circuit breaker is to be tripped open inresponse to a fault condition. The coil I1 of the fault responsive relayindicated at Il is energized in response to a fault condition to closethe contacts at Il by downward movement of the relay coil plunger I9.The tripping control circuit is thereupon energized from the controlsource 20 through the relay contacts I 8, the latch tripping coil 2| andthe contacts 22 of the so-called auxiliary aswitch. Upon energization ofthe trip coil 2 I the plunger 2 I is projected toward the left to causeclockwise rotation of a lever 23 and corresponding rotation of the latchI3 thereby causing release of the breaker rod II and opening of thebreaker. The lever 23 is co-pivotally mounted at I3 with the latch I3and is disengageably related thereto by an oiset portion 23 arranged toengage an extension I3" of the latch. The breaker is now open and theroller I2 of the lever 8 rests on the upper end of the plunger 'I.

'The breaker closing operation is performed in the following manner.`Assuming now that no fault condition exists, the relay I1 due to itsspring bias at II closes the closing circuit contacts at 24 so that whenthe closing button is pressed bylthe operator to close the contacts at25 the operating coil 26 of the valve 6 is enervgized from the controlsource 20 through the contacts 24 and 25, the pressure indicating aux-Viliary switch 21 and the contacts of the limit switch 2B. When theplunger 2l' of the valve solenoid is moved toward the right, itcompletes a holding circuit at the contacts 26" so that the closingoperation can be completed notwithstanding but momentary closure of theclosing button. Simultaneously the slide valve member 29, which isreciprocally operable within the valve housing I0 and is normally biasedat II toward closed position, is moved to uncover the port 32 therebyestablishing fluid connection between the source I and the cylinder I.Admission of iiuid under pressure to the working` face of the piston lresults in upward movement of the piston and corresponding closingmovement of the lever 3 and breaker rod .I I.

' This closing movement constitutes a strong high speed closing thrustthat is effective to close the circuit breaker against the usual springand contact resistance, at which time the latch I3 is snapped by itsspring ilbeneath the breaker rod roller II to hold the breaker in theclosed position. It will be noted that when the-piston l is lnear theupper limit of its travel, it engages the is coveredv by 4the left-handportion of the valve member. i

In the operation so far described, it has been assumed that no faultcondition existed that required trip-free operation during the closingstroke. Let it nowbe assumed that the fault condition which caused theinitial tripping and open-el ing of the circuit breaker has not beencorrected and that the operative attempts to close the circuit breakerwhile the fault condition exists. The closing operation is initiated inthe manner above described. However, when the breakeinears the end ofthe closing stroke as the breaker contacts first engage (the a switchnow being closed), the fault responsive relay I1 will cause actuation ofthe tripping solenoid 2| and clockwise movement of the lever 23. Thislever, it will be noted, not only causes rotation of the latch Il to anonlatching position but also engages the extension 33' of a dump valve33 to cause immediate venting of the cylinder 5 to atmosphere through acomparatively large port 34.

It will therefore be observed that when the dump valve 33 fis open thepiston I is no longer acted upon by a closing force since the operatingK pressure is practically instantly dissipated even though the valve 8still be open. In fact, the piston l can move to its initial positionnotwithstanding the continued flow of fluid from the source I by reasonci' the free venting at the dump valve.l With this 'arrangement'. themechanism is completely trip-free during the closing operation and thetrip-free operation is `moreover'` instantly responsive to the faultcondition for permitting the circuit breaker immediately to return toits open circuit position. The dump valve 33 is spring biased at 35toward `its normally closed position as shown. I

It should be understood that my invention'is4 not limited to specificdetails of construction and arrangement thereof herein illustrated. andthat changes and modifications may occur te one skilled in ,the artwithout departingl from the spirit of my invention. Y

What I claim as new and desire to secure Aby Letters Patent of theUnited States is:

1. A fluid pressure operating mechanism of the,y trip-free type for anelectricl circuit breaker comprising a source of iiuid pressure, a iluidmotor including a piston and cylinder, means disengageably relating saidpiston to said' circuit breaker for closing said breaker, a latch forholding said circuit breaker in closed position independently of saidpiston so that said piston canv return to its initial open positionwhereby said circuit breaker-'is normally free to tripopen at high speedindependently of said piston, a dump valve for venting said cylinder toatmosphere at the working face of said piston whereby said piston canalso return to its initialposition during a closing operation, and faultresponsive means for releasing said latch to cause opening movement ofsaid breaker and for also opening said dump valve for causing trip-freeoperation.

2. A pneumatic operating mechanism of the trip-free type for an electriccircuit breaker comprising a source of compressed air, an operatingcylinder and piston arranged to be' connected through a control valve tosaid source,lmeans disengageably relating said piston to said circuitbreaker including a linkage, a latch for holding said linkage in closedcircuit position, a dump valve for venting at high speed the pressure insaid cylinder on the working side of said piston, an'actuating membercommon to said latch and said dump valve, and fault responsive meansoperatively related to said common actuating member for causingsubstantially simultaneous release of said latch and opening of said.dump valve for trip-free operation.

3. Apneumatic operating mechanism of the trip-free type for an electriccircuit breaker comprising a source of compressed gas, a iluid motorincluding a piston and cylinder, a control valve between said source andcylinder, said valve being` arranged to admit gas under pressure fromsaid source to said cylinder and also directly to vent said cylinder toatmosphere, means operatively relating said piston to said circuitbreaker for closing said breaker, a latch for holding said ciropeningmovement oi' said breaker and for also opening said dump valve forcausing trip-free operation.

4. A pneumatic operating mechanism of the trip-free type for an electriccircuit breaker comprising asource of compressed gas, an operatingcylinder and piston arranged to be connected through a control valve tosaid source. a lever arranged to be disengageablyv engaged by saidpiston for closing said circuit breaker, a latch for holding said leverin closed circuit position whereby said piston can return to its initialposition after closing said breaker, a dump valve for venting at highspeed the pressure in said cylinder on the working side of said pistonnotwithstanding continued fiowp'f gas from said source, actuating meanscommonsaid latch and said dump valve, and fault responsive means oper-.-`atively related to said common actuating means for causing trip-freeoperationz'by substantially simultaneous release of said latch andopening of said dump valve.

'5. A fluid pressure operating mechanism of the trip-free type for anelectric circuit breaker comprising a sourceof fluid pressure, afiuidmotor arranged to be connected to said source, means operativelyrelating said motor to saidA circuit breaker for closing said breaker, alatch for holding closed said breaker, a dump valvefor instantly ventingsaid ,uid motor to permit high speed reversal thereof, said dump valveand latch being Vmechanically interrelated, and a tripping solenoidoperative both to release said latch and to open said dump valve fortripfree operation of said breaker.

ducing a closing operation of said breaker, a

source of fluid under pressure for operating said motor, a control valveforconnecting said source of fluid with said iluid motor for closingsaid circuit breaker, a latch for holding closed saisi-y breaker, and adump valve directly connected to said fluid motor apart from theconnection to said pressure source operable upon the opening movement ofsaid circuit breaker for instantaneously reducing the back pressureagainst said uid motor so that high-speed-opening operation of saidcircuit breaker may be obtained. HAROLD E. STRANG.

